Localization refers to determining the location of a mobile user terminal such as a mobile phone, tablet or laptop computer, typically in terms of geographic position relative to the surface of the earth.
Various location technologies are known for performing localization. One type of location technology is satellite based positioning, for example GPS (Global Positioning System) (including variants such as assisted GPS or differential GPS), GLONASS (Global Navigation Satellite System) or Galileo. Another type is based on trilateration or multilateration from base stations of a mobile cellular network, for example E-OTD (Enhanced Observed Time Difference) or OTDOA (Observed Time Difference of Arrival). Other types include systems which work by reference to a known location of an access point of a WLAN (wireless local area network), perhaps also taking into account signal strength received from the access point; and systems such as Geo IP based on a mapping between network addresses and geographic locations.
Each technology has its own limitations, and any given system may or may not be available to a given mobile terminal at any given time, or for other reasons may or may not be fully exploited by a given mobile terminal.